In cryptography or computer security, a certificate is an electronic document used to prove the existence of a relationship. As an example, a certificate may be used to prove that a relationship exists between a public key and an email address associated with the owner of the public key. The certificate includes information about the key, information about the entity that owns the key, and the digital signature of an entity that has verified the accuracy of the certificate's contents. If the digital signature is valid and the signer is trusted, then the key can be used to communicate with its owner. Typically, the entity providing the digital signature is a certificate authority, such as a trusted third party company that charges customers to issue certificates. However, in certain cases, the certificate is not signed by a trusted certificate authority. For example, the certificate may be self-signed, which means the entity providing the digital signature is the same as the entity that the certificate identifies as the owner of the key. As another example, the certificate may be signed by a certificate authority that is unknown or otherwise untrusted. A certificate can present security risks, particularly if it is not verified by a trusted certificate authority.